The Shadow  started out as a mysterious voice on the radio, created by the publisher Street & Smith and brought to life by writer Walter B. Gibson. Gibson turned that voice into a full-blown character in 1931, and The Shadow soon jumped into all kinds of media—American comic books and strips, movie serials, video games, and at least five feature films. On radio, some episodes even featured Orson Welles in the lead.

(From Wikipedia)

The Zero Hour (aka Hollywood Radio Theater) was a 1973–74 American radio drama anthology series hosted by Rod Serling.^[1][2] With tales of mystery, adventure and suspense, the program was broadcast for two seasons.

Yours Truly, Johnny Dollar was a radio drama that aired on CBS Radio from February 18, 1949 to September 30, 1962.

CBS Radio Mystery Theater (a.k.a. Radio Mystery Theater and Mystery Theater, sometimes abbreviated as CBSRMT) is a radio drama series created by Himan Brown that was broadcast on CBS Radio Network affiliates from 1974 to 1982, and later in the early 2000s was repeated by the NPR satellite feed.